Add support for Websocket protocols.

runtime/bin/socket_patch.dart

Index: runtime/bin/socket_patch.dart
diff --git a/runtime/bin/socket_patch.dart b/runtime/bin/socket_patch.dart
index 789dd001399664a3632d3f8e33467a49e198f5bb..1480f1f97b41ef2331744cca1e9313d799dddfc4 100644
--- a/runtime/bin/socket_patch.dart
+++ b/runtime/bin/socket_patch.dart
@@ -615,7 +615,9 @@ class _NativeSocket extends NativeFieldWrapperClass1 {
       if (isClosedRead) {
         close();
       } else {
+        bool connected = eventPort != null;
         sendToEventHandler(1 << SHUTDOWN_WRITE_COMMAND);
+        if (!connected) disconnectFromEventHandler();
       }
       isClosedWrite = true;
     }
@@ -626,7 +628,9 @@ class _NativeSocket extends NativeFieldWrapperClass1 {
       if (isClosedWrite) {
         close();
       } else {
+        bool connected = eventPort != null;
         sendToEventHandler(1 << SHUTDOWN_READ_COMMAND);
+        if (!connected) disconnectFromEventHandler();
       }
       isClosedRead = true;
     }